Gl. Roisman et al., Decreased expression of angiotensin-converting enzyme in the airway epithelium of asthmatic subjects is associated with eosinophil inflammation, J ALLERG CL, 104(2), 1999, pp. 402-410
Background: Angiotensin-converting enzyme (ACE) is a peptidase involved in
the metabolism of several bioactive peptides. It may be involved in the air
way inflammation and hyperresponsiveness that occur in asthma.
Objective: We studied the expression of ACE in the airway mucosa of normal
and asthmatic subjects and assessed the relationship between ACE expression
and airway inflammation and bronchial hyperresponsiveness in asthma.
Methods: We used immunohistochemistry to study the ACE expression and airwa
y inflammation in bronchial biopsy samples obtained by fiberoptic bronchosc
opy from 20 asthmatic subjects randomly assigned to groups treated with (n
=10) or without inhaled corticosteroids (n = 10) and from normal subjects (
n = 10). Airway response to methacholine and bradykinin was also determined
for all subjects.
Results: In normal subjects ACE was present in the surface epithelium, the
endothelial cells of the lamina propria, and the submucosal glands, in whic
h ACE was found in seromucous cells and in secreted mucus. ACE was not dete
cted in smooth muscle cells and in most of the endothelial cells of the vas
cular network surrounding the glands. ACE was absent or present at lower le
vels in the surface epithelium of asthmatic subjects not treated with corti
costeroids compared with those treated with corticosteroids and the control
group. In asthmatic subjects low levels of ACE in the epithelium were asso
ciated with larger numbers of eosinophils in the epithelium and lamina prop
ria. There was no relationship between ACE levels in the airway mucosa and
airway responsiveness to methacholine and bradykinin.
Conclusion: ACE expression is decreased in the epithelium of asthmatic pati
ents and is associated with increased eosinophil inflammation.